It is conventional practice to form photographic elements by forming on a support one or more photographically active layers. Typically these photographically active layers contain silver halide dispersed in a hydrophilic colloid, such as gelatin, to form an emulsion. In multi-layer photographic elements used in color photography there are at least three selectively sensitive color-forming units each made up of one or more emulsion layers coated on one side of a photographic support, such as film or paper. The color forming units are typically rendered variously responsive to the red, green and blue regions of the spectrum. The blue-sensitive color-forming unit typically contains a yellow coupler, the green-sensitive color forming unit a magenta coupler and the red-sensitive color forming unit a cyan coupler. In an alternative form color couplers are not initially present in the photographic element, but are introduced during processing after an image forming exposure. Hydrophilic colloid subbing layers, interlayers and protective layers are also typically present. The blue-sensitive color forming unit forms preferably the outermost unit, and a yellow filter layer normally overlies the green and the red sensitive color forming units to protect them against residual blue light not absorbed in the blue-sensitive color forming unit. Multi-layer photographic elements used in color photography of this general type and processes for their preparation are well known in the art.
An alternative color dye forming color photographic element can also be formed from a plurality of light sensitive silver halide emulsion layers wherein each light sensitive silver halide emulsion layer is sensitized to the entire visible spectrum and comprises cyan dye forming couplers, magenta dye forming couplers and yellow dye forming couplers. The object of this photographic element is to produce a neutral record suitable for producing black and white prints. These films are typically referred to as chromogenic films and are processed by conventional color negative film processors.
It is conventional practice to incorporate into photographic hydrophilic colloid layers addenda, referred to as hardeners, having as their purpose the reduction or elimination of the susceptibility of such colloid layers to wet abrasion, swelling in aqueous solutions and softening at elevated temperatures. Wet abrasion, swelling and softening are of primary concern during processing, especially in those instances where it is desired to accelerate processing by resort to elevated temperatures. Gelatin containing layers that are not treated with a hardening agent generally have poorer water resistance, heat resistance, and wet abrasion resistance.
After exposure to light, the photographic element is processed chemically to reveal a usable image. The chemical processing entails two fundamental steps. The first is the treatment of the exposed silver halide with a color developer wherein some or all of the silver halide is reduced to metallic silver while an organic dye is formed from the oxidized color developer. The second is the removal of the silver metal thus formed and of any residual silver halide by the desilvering steps of (1) bleaching, wherein the developed silver is oxidized to silver salts; and (2) fixing, wherein the silver salts are dissolved and removed from the photographic material. The bleaching and fixing steps may be performed sequentially or as a single step. The overall rate of development is influenced by swelling of the gelatin layer and diffusion rate of different chemical species into and out of the swollen emulsion layers. The diffusion coefficient value and emulsion layer swelling thickness increases with processing temperature and decreases with increasing hardness of the gelatin. When emulsion layer is hardened, the decrease in diffusivity is partially offset by the decrease in the swelling thickness and hence the decrease in diffusion pathlength. Therefore under given processing conditions, there is an optimum emulsion layer hardness for achieving desirable optical density or contrast or photographic speed. For this reason, it is desirable that the hardening reaction be complete shortly after layer formation. That is, the coatings attain their complete functionality, based on hardening, immediately after manufacture. This avoids changes in photographic properties as a result of the so-called "afterhardening".
Afterhardening causes sensitized photographic materials to be held until the completion of hardening, at which time, the best sensitometric corrections are made. However, the corrections may vary with coating events, manufacturing processes, and significantly increase manufacturing cycle time and cost. Many efforts have been made to develop fast acting hardeners to allow coatings to reach their maximum hardness at the time of coating. However, fast acting hardeners are known to initiate viscosity increase and premature gelation that lead to disruptions in the coating process.
From an environmental point of view, it is desirable to reduce the amount of silver, couplers, and solvents incorporated in the emulsion layers to lower chemical usage and reduce undesirable effluents. In addition, it is highly desirable to process a photographic material as rapidly as possible, and an accelerated process is constantly being sought.
The object of this invention is to provide a multilayer, multicolor photographic element that has well-balanced water swelling values in each dye-forming hydrophilic colloid containing silver halide emulsion layer, that has improved sensitometric properties immediately after manufacturing, has lower chemical usage, and has reduced afterhardening effect during storage of the element.